Get all added, deleted or modified keys. DictDelata implements this in a stateful fashion.

DictDelta.py

class DictDelta:
    '''Returns a list of ḱeys, which are added, deleted or whose values have been altered compared to the dict passed in the previous call.'''

    def __init__(self):
        self.old_dict = None

    def __call__(self, new_dict):
        """Returns list of changed keys."""

        # explicitly check for None, prevent all keys being returned on 1st run
        if self.old_dict is None:      
            self.old_dict = new_dict
            return []

        changeset = self.diff_keys(new_dict, self.old_dict)
        self.old_dict = new_dict
        
        return  changeset

    def diff_keys(self, d1, d2):
        ...

diff_keys.py

def diff_keys(d1, d2):
    """Diff dicts via set operations and subsequent traversing value comparison.
    """
    changed_keys = []
    d1_keys = set(d1.keys())
    d2_keys = set(d2.keys())
    
    sym_diff = list(d1_keys ^ d2_keys)
    changed_keys.extend(sym_diff)
    
    intersec = d1_keys & d2_keys
    for k in intersec:
        if type(d1[k]) is dict:
            changed_keys.extend(self.diff_keys(d1[k], d2[k]))
        elif d1[k] != d2[k]:
            changed_keys.append(k)
            
    return changed_keys